1. Field of the Invention
The present invention relates a system and method for IP Video distribution and protection that is lower cost by using a reduced number of expensive IP multi-cast router high-speed ports.
2. Background of the Prior Art
Internet Protocol Television (IPTV) describes a system where a digital television service is delivered using the Internet Protocol over a network infrastructure, which may include delivery by a broadband connection. For residential users, IPTV is often provided in conjunction with Video on Demand and may be bundled with Internet services such as Web access and VoIP. IPTV is typically supplied by a broadband operator using a closed network infrastructure, or it may be delivered over the public Internet.
Typically, IPTV services are multi-cast, which is delivery of information to a group of destinations simultaneously by delivering the messages over each link of the network only once and by only creating copies when the links to the destinations split. IPTV is multi-cast using IP Multi-cast technology, which is the implementation of the multi-cast concept on the IP routing level. IP multi-casting is performed by multi-cast routers, which determine distribution paths for data traffic sent to a multi-cast destination addresses.
While a number of network architectures may be used to deliver IPTV, optical networks are particularly advantageous due to their high data traffic capacity. Popular optical network technologies include synchronous optical networks and passive optical networks. Common synchronous optical networking technologies include SONET and SDH technologies. Synchronous networking requires that the exact rates that are used to transport the data are tightly synchronized across the entire network. This synchronization system allows entire inter-country networks to operate synchronously, greatly reducing the amount of buffering required between each element in the network. Both SONET and SDH can be used to encapsulate earlier digital transmission standards, or used directly to support either ATM or so-called Packet over SONET/SDH (POS) networking.
Another architecture that may form at least a portion of a network used to deliver IPTV is a Passive Optical Network (PON). A PON is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises, typically 32. A PON consists of an Optical Line Termination (OLT) typically at the service provider's central office and a number of Optical Network Units (ONUs) near end users. A PON configuration reduces the amount of fiber and central office equipment required compared with point to point architectures. Downstream signals are broadcast to each premise sharing a fiber. Encryption is used to prevent eavesdropping; however, IP Multicast signals are NOT encrypted. Upstream signals are combined using a multiple access protocol, typically time division multiple access (TDMA). The OLTs “range” the ONUs in order to provide time slot assignments for upstream communication and to compensate for round-trip transmission delay differences between ONU's on a specific PON and the shared OLT
Typically, synchronous optical networks and passive optical networks are both used together in the multi-cast of IPTV services. One problem that has arisen with such architectures is that they typically require the use of a large number of expensive high speed ports on the multi-cast routers, especially when protection paths are provided. A need arises for a technique by which IP Video distribution and protection can be provided that is lower cost by using a reduced number of expensive IP multi-cast router high-speed ports.